While President Trump announced Friday that he is “immediately” canceling Obama’s deal with Cuba, the reversal relies on regulations that could take months — or years — to finalize.

Trump said he will strictly enforce the prohibition against Cuban travel for tourism using rules that provide only 12 reasons, such as family visits, educational activities and athletic competitions, for entering the country.

“Our new policy begins with strictly enforcing U.S. law,” Trump said. “We will enforce the ban on tourism.”

Ultimately, Trump proposed to block travel that benefits the Cuban military, intelligence or security services. In order to accomplish that, individual travel would be prohibited — people visiting the country would need to go in groups.

The detailed regulatory proposals weren’t released Friday. Trump's national security memo on Cuba asked the departments of Treasury and State to develop regulations within 30 days. The rules would then be published for public comment and possible revisions.

The Treasury Department, which licenses Cuba travel, said in a statement that individual travel will no longer be allowed for purposes such as education under pursuit of an academic degree. "The traveler’s schedule of activities must not include free time or recreation in excess," the department said.

Instead, the department will authorize group travel under the auspices of an organization that maintains a full-time schedule of activities that enhance contact with Cuban people, support civil society and promote independence from Cuban authorities.

Airlines competed to provide flights after the Obama administration initiated a resumption in diplomatic relations between the countries for the first time in more than 50 years. Airlines had provided charter flights for decades, but the restoration of ties allowed the resumption of scheduled service considered key for business and personal ties.

“Delta Air Lines will adhere to any changes in the regulations announced by the Trump administration regarding travel to Cuba,” the carrier said.

Leigh Barnes, regional director for Intrepid Travel, a tour company which has brought 714 American passengers to Cuba in 47 trips since 2015, said tour operators would face stricter government audits about travelers belonging to the 12 allowed categories. But Barnes expected airlines to continue scheduled flights to Cuba, rather than revert to charter flights, as travelers adapt their plans to join person-to-person tour groups.

"While demand for commercial flights remains to be seen, historically, the airlines have done well to manage their yields by shifting to smaller planes or slightly lower frequency of departures,” Barnes said. “There are still a lot of meaningful tourism offerings for American travelers. We expect airlines to keep servicing these routes and we are excited to continue welcoming American travelers to Cuba."